Not Applicable
Not Applicable
1. Field of the Invention
The invention relates to a digital transmission system comprising at a transmitting end data coding means based on a binary block code defined by a parity check matrix, and at a receiving end decoding means for making decisions on received data.
The invention also relates to a method of decoding previously coded data based on a binary block code defined by a parity check matrix and a decoder for decoding previously coded data based on the binary block code defined by a parity check matrix.
The invention has important applications, notably in the field of digital data transmission.
2. Description of Related Art
The article xe2x80x9cA Class of Algorithms for Decoding Block Codes with Channel Measurement Informationxe2x80x9d, written by David Chase and published in IEEE Transactions on Information Theory, Vol. IT-18, no. 1, January 1972, describes a method of decoding binary block codes.
It is an object of the invention to propose a much simpler method which enables to obtain a performance of the same order.
For this purpose, a digital transmission system according to the invention and as described in the opening paragraph is characterized in that said decoding means are iterative decoding means, each iteration corresponding to the decoding, for received data, of the code or codes defined by a row of the matrix.
Similarly, a decoding method according to the invention and as described in the opening paragraph is characterized in that said method is an iterative decoding method which comprises for each iteration a decoding step, for received data, of the code or codes defined by a row of the matrix.
And a decoder according to the invention and as described in the opening paragraph is characterized in that it comprises iterative decoding means, each iteration corresponding to the decoding, for received data, of the code or codes defined by a row of the matrix.
When said binary block code is an extended code, each row of the matrix defines two separate codes and, advantageously, said iterative decoding means comprise means for processing each of the two codes in parallel.
Finally, in an advantageous embodiment of the invention, said decoding means comprise for the processing of certain iterations at least:
calculating means for calculating, based on input data, reliability data relating to soft decisions,
transforming means for calculating transformed data based on said soft decisions so as to normalize the mean value of said reliability data,
weighting means for calculating weighted sums of said transformed data and received data with a first and a second weight factor, respectively,
generating means for generating subsequent input data to be re-inserted for the next iteration on the basis of said weighted sums.